Aussie model didn't know she was pregnant until she gave birth

An Australian model had no idea she was pregnant until she gave birth unexpectedly two weeks ago.

Erin Langmaid, 23, was still fitting into her size 8 skinny jeans when she was 37 weeks pregnant with her daughter, but the Melbourne-based mum had no clue she was even expecting.

A model with Neon Model Management, Erin posed for photoshoots and donned form-fitting outfits without ever noticing any changes to her body.

Erin Langmaid didn't know she was pregnant until she moment she gave birth. (Instagram)

She had no baby bump, no morning sickness and no cravings, and was having contraception injections throughout, though admits she wasn't always "up to date" with them.

Still, when Erin woke with painful cramps on October 29, Erin never guessed she was going into labour.

"There was nothing to indicate [to me] like, 'oh, I might be pregnant'," she tells 9Honey, adding that she assumed it was her period coming.

"I [thought], 'surely not, this can't be happening.'"

Explaining that her cycle has always been "super irregular", Erin had experienced spotting but no true periods during the nine months of her pregnancy, though she says that's not out of the ordinary for her and "didn't sound any alarm bells."

She called in sick to work but the cramps only got worse over the course of the day, and by the time her partner, Dan Carty, got home that night Erin was in serious pain.

She and Dan named their daughter Isla, but admit they weren't at all prepared for her. Family and friends rallied around the young couple, collecting baby supplies and clothes for them while Erin recovered in hospital.

And despite having "no idea how to be parents", Erin says she and Dan have been taking things one day at a time and learning as they go.

Though she and Dan had mentioned kids in passing, it had always been a plan for "further down the line" and they'd never seriously discussed parenthood.

Baby Isla is happy and healthy, Erin saying she felt immediate love for her daughter. (Instagram)

Now back at home, the pair are adapting to life with Isla and Erin has been relying on friends with small children of their own for advice.

"I've been picking their brains on every little thing and they've been amazing," she says, adding they're her biggest resource.

"There are so many little things that you don't even think of until [they] happen. There are questions you don't know to ask until it comes up."

And though she's taking to motherhood well, Erin isn't planning to make Isla a big sister any time soon.